This invention relates to expansion valves for refrigeration systems, and in particular, to an electrically operated expansion valve. While the invention is described in particular detail with respect to expansion valve applications, those skilled in the art will recognize the wider applicability of the inventive principles described hereinafter.
Refrigeration systems generally include an evaporator, a compressor, and a condenser. Refrigerant vapors drawn from the evaporator by the compressor are forced into the condenser, where the vapor liquifies. The liquid refrigerant then is returned to the evaporator through an expansion valve. The expansion valve converts the refrigerant from a high pressure liquid to a low pressure vapor plus liquid by passing the refrigerant through a restriction in the valve. Control of refrigerant input to the evaporator can be maintained by inserting a valve member in the restriction of the expansion valve, and adjusting the valve member positioned in response to a particular external condition.
Presently, thermostatic expansion valves are utilized extensively for refrigerant control. While working for their intended purpose, thermostatically controlled valves are relatively complicated in their manufacture. In addition, in heat pump applications, two valves are required, as generally speaking the valves must be adjusted to the corresponding refrigerant coil with which they operate.
To overcome these deficiencies, electrically controlled expansion valves have been developed. One particular valve for refrigerant systems is described in the U.S. Pat. to Kunz, No. 3,967,781, assigned to the assignee of the present invention. The Kunz patent discloses a valve utilizing a heat motor to control the valve stem position, and consequently, valve operation. The valve disclosed in Kunz U.S. Pat. Nos. 3,967,781 was primarily designed for conventional refrigeration systems in which the fluid flow to the valve is in a single direction. When the valve disclosed in U.S. Pat. No. 3,967,781 is employed in heat pump applications, that is, in applications where fluid through the valve passed in two directions, several problems with valve operation are encountered. While the valve would operate satisfactorily for controlling flow in one direction through the valve, the passage of fluid in the opposite direction often resulted in leakage from the valve body to the heat motor. That is to say, the reversal of the high pressure and low pressure sides of the valve places high pressure fluid on a side of the valve stem normally at low pressure in one way flow applications. Fluid leakage to the heat motor generally is the result. Such leakage causes malfunction in heat motor operation, with consequent eratic operation of the valve.
The invention disclosed hereinafter overcomes the deficiencies encountered with electrically operated valves in heat pump applications, by incorporating a number of protective features designed to prevent refrigerant flow into the heat motor of the valve. While these improvements were designed primarily for heat pump applications, the valve may find application in other two-way systems, and of course, also may be used in conventional one-way flow systems including conventional refrigeration systems.
One of the objects of this invention is to provide an improved electrically operated control valve.
Another object of this invention is to provide an electrically operated valve for heat pump applications.
Another object of this invention is to provide an expansion valve compatible with heat pump applications, the operation of which is dependent solely on an electrical input.
Another object of this invention is to provide an electrically operated valve for refrigeration control incorporating means for preventing fluid leakage to the electrically controlled apparatus of the valve.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.